{"id":2212,"date":"2026-08-21T17:14:38","date_gmt":"2026-08-21T09:14:38","guid":{"rendered":"https:\/\/zishengtransformer.com\/?p=2212"},"modified":"2026-08-21T17:14:38","modified_gmt":"2026-08-21T09:14:38","slug":"transformer-failures-causes-analysis","status":"publish","type":"post","link":"https:\/\/zishengtransformer.com\/ar\/transformer-failures-causes-analysis\/","title":{"rendered":"\u0644\u0645\u0627\u0630\u0627 \u062a\u062d\u062f\u062b \u0623\u0639\u0637\u0627\u0644 \u0627\u0644\u0645\u062d\u0648\u0644\u0627\u062a\u061f \u062a\u062d\u0644\u064a\u0644 \u0644\u0623\u0647\u0645 \u0627\u0644\u0645\u0634\u0643\u0644\u0627\u062a \u0641\u064a \u0627\u0644\u0627\u062e\u062a\u064a\u0627\u0631 \u0648\u0627\u0644\u062a\u0634\u063a\u064a\u0644 \u0648\u0627\u0644\u0635\u064a\u0627\u0646\u0629 \u0627\u0633\u062a\u0646\u0627\u062f\u064b\u0627 \u0625\u0644\u0649 \u062f\u0631\u0627\u0633\u0627\u062a \u062d\u0627\u0644\u0627\u062a \u0645\u064a\u062f\u0627\u0646\u064a\u0629"},"content":{"rendered":"
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Transformer failures are a frequent headache for power distribution projects, especially in harsh operating environments across Africa and the Middle East. Many site operators face unexpected shutdowns, costly repair work and long power outages due to avoidable transformer faults. Based on our on\u2011site service experience, this article breaks down the main root causes behind transformer failures and offers actionable technical guidance for field engineers and project buyers.\r\n<\/code><\/pre>\n
\"transformer<\/p>\n
Over the past few years, while participating in on-site services for industrial, renewable energy, and power distribution projects, Zisheng Electric engineers have observed a recurring phenomenon: the issues that truly cause unplanned downtime<\/strong> are often not sudden equipment failures. Instead, they usually start from small problems that seem insignificant during commissioning \u2014 issues that are overlooked during installation, gradually worsen after three to five years of operation, and eventually develop into failures. The overall losses can far exceed the cost of a new transformer.<\/p>\n
Saudi Arabia Commercial Complex, 1250kVA Dry-Type Transformer<\/strong><\/h3>\n
The transformer operated normally for the first two years. Starting from the third summer, frequent temperature control alarms<\/strong> began to occur.<\/p>\n
All factory test parameters were qualified, but the installation location was in an underground equipment room. The building\u2019s air-conditioning system mainly served commercial areas and did not provide dedicated ventilation for the transformer room.<\/p>\n
When outdoor temperatures reached 45\u2103 in summer, heat continuously accumulated inside the equipment room, causing the transformer to operate near its temperature rise margin<\/strong> for extended periods.<\/p>\n
Northern Chile 50MW Solar PV Project, 35kV Compact Transformer<\/strong><\/h3>\n
After approximately one and a half years of operation, the site maintenance team discovered during quarterly oil sample testing that the acetylene content in the transformer oil of one unit showed a continuous increasing trend.<\/p>\n
The initial data had not yet reached the alarm threshold, but after reviewing historical trends, we determined that this change could not simply be considered random fluctuation.<\/p>\n
The transformer passed all factory tests, and protection devices had never operated.<\/p>\n
The Atacama Desert in Chile experiences extreme temperature differences between day and night. Each day, the photovoltaic system goes through a cycle of:<\/p>\n
Morning rapid load increase \u2192 Noon full power generation \u2192 Evening sudden reduction to no load.<\/p>\n
The accumulated mechanical and thermal stresses caused winding support blocks to loosen, minor coil displacement, and reduced tightening force at leads and connections.<\/p>\n
After component micro-movement, friction, and poor contact occurred, localized arc discharge was triggered, generating acetylene<\/strong>.<\/p>\n
South Africa Industrial Processing Plant<\/strong><\/h3>\n
The transformer capacity was initially designed based on the original load demand. Two years later, new production lines were added, causing the load rate<\/strong> to remain above 90% for extended periods.<\/p>\n
Due to the long expansion cycle of the local power grid, the company had no choice but to continue operating under high load conditions.<\/p>\n
By the fifth year, the transformer\u2019s insulation performance<\/strong> had significantly deteriorated, eventually requiring shutdown and maintenance.<\/p>\n
Site personnel often ask:<\/p>\n
\u201cIs there a problem with the transformer quality?\u201d<\/p>\n
However, from an engineering perspective, most failures cannot simply be attributed to the manufacturing side.<\/p>\n
Many problems occur before the equipment is even energized \u2014 due to insufficient design inputs<\/strong>, inadequate evaluation of installation conditions<\/strong>, and missing or ineffective operation management<\/strong> later in the equipment lifecycle.<\/p>\n
A transformer expected to operate reliably for more than 20 years in real-world conditions is not running in a temperature-controlled laboratory. It must withstand:<\/p>\n
    \n
  • Outdoor temperatures exceeding 45\u2103 in summer;<\/li>\n
  • Dust accumulation and poor ventilation in substations;<\/li>\n
  • Grid voltage fluctuations<\/strong> and lightning surge impacts<\/strong>;<\/li>\n
  • High loading rates running continuously day and night;<\/li>\n
  • Frequent changes of maintenance personnel;<\/li>\n
  • Loss of operation records.<\/li>\n<\/ul>\n
    The reliability of a transformer is not determined only by its factory test report. The real question is whether it can withstand the \u201cinvisible stresses\u201d it faces on site.<\/p>\n
    Below, based on our accumulated field experience from industrial, renewable energy, and commercial building projects, we will analyze several common transformer failures \u2014 from their failure mechanisms<\/strong>, early detection methods<\/strong>, to fundamental prevention measures<\/strong> \u2014 and explain them as practically as possible.<\/p>\n
    1. Abnormal Temperature Rise: The Most Common \u201cChronic Disease\u201d \u2014 Usually Not a Manufacturing Quality Issue<\/strong><\/span><\/h2>\n
    \"\"<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
    \n
    \n
    \n
    \n
    1.1Case: Saudi Arabia Industrial Project \u2014 2500kVA Oil-Immersed Transformer<\/strong><\/h3>\n
    The project installed one 2500kVA oil-immersed transformer. The designed capacity met the initial production requirements, losses complied with IEC 60076, and all factory tests were successfully passed.<\/p>\n
    Six months after commissioning, the owner reported frequent temperature alarms<\/strong> during the high-temperature period every afternoon.<\/p>\n
    Site inspection findings:<\/strong><\/p>\n
      \n
    • Actual load verification: during the afternoon production peak, the load rate<\/strong> reached approximately 95%;<\/li>\n
    • Installation environment inspection: installed on an outdoor platform, with summer maximum temperatures exceeding 45\u2103. The transformer was exposed to direct sunlight, surrounding dust accumulation was significant, and visible dust buildup was found on the surface of the radiators<\/strong>;<\/li>\n
    • Operating data review: the transformer operated under high load continuously for several hours every day.<\/li>\n<\/ul>\n
      Conclusion:<\/strong>
      This was not a manufacturing defect. The high ambient temperature<\/strong> + reduced heat dissipation caused by dust accumulation<\/strong> + long-duration high-load operation<\/strong> together resulted in abnormal temperature rise<\/strong>.<\/p>\n
      1.2Why Does a Transformer Overheat Even When the Capacity Is \u201cSufficient\u201d?<\/strong><\/span><\/h3>\n
      This is a common selection mistake.<\/p>\n
      The rated capacity on the nameplate does not mean the transformer can always operate at full load under any environmental condition.<\/p>\n
      A 1000kVA transformer represents the rated capacity under standard reference conditions<\/strong>:<\/p>\n
        \n
      • Maximum ambient temperature: 40\u2103;<\/li>\n
      • Altitude: \u22641000m;<\/li>\n
      • Harmonic conditions within standard limits.<\/li>\n<\/ul>\n
        A rough estimation:<\/p>\n
        Standard transformer design usually considers a 40\u2103 ambient temperature. If the actual environment reaches 45\u2103, the temperature rise margin<\/strong> is immediately reduced by 5K.<\/p>\n
        If the transformer operates at 100% load continuously, the winding temperature rise<\/strong> may exceed the design value by 8\u201310K.<\/p>\n
        When these two factors are combined, the actual operating temperature may exceed the design limit by more than 10\u2103.<\/p>\n
        Higher temperature is not just an alarm issue \u2014 it directly causes service life reduction<\/strong>.<\/p>\n
        The thermal aging<\/strong> of oil-immersed transformer insulation follows the \u201c10-degree rule\u201d<\/strong>:<\/p>\n
        Every 10\u2103 increase in operating temperature approximately reduces insulation life by half.<\/p>\n
        A transformer designed for a 20-year service life may approach the end of its insulation life within only 8\u201310 years if it operates above temperature limits for long periods.<\/p>\n
        1.3From an Engineer\u2019s Perspective, Practical Solutions to Overheating<\/strong><\/span><\/h3>\n
        \uff081\uff09 Capacity Design Should Not Only Consider Current Load<\/strong><\/span><\/h4>\n
        For commercial buildings, industrial plants, and data centers, it is recommended to reserve 15%\u201320% capacity margin<\/strong> based on calculated load.<\/p>\n
        If the owner has a clear expansion plan, select transformer capacity according to the future expanded load directly.<\/p>\n
        \uff082\uff09 Quantitatively Evaluate Heat Dissipation Conditions Instead of Simply Saying \u201cGood Ventilation\u201d<\/strong><\/span><\/h4>\n
        Outdoor installation without obstruction:<\/strong><\/p>\n
          \n
        • Provides the best natural ventilation;<\/li>\n
        • However, solar radiation and rain protection must also be considered.<\/li>\n<\/ul>\n
          Indoor substation room:<\/strong><\/p>\n
            \n
          • Calculate room volume;<\/li>\n
          • Verify louver area;<\/li>\n
          • Confirm exhaust fan airflow capacity.<\/li>\n<\/ul>\n
            Basement or mezzanine installation:<\/strong><\/p>\n
              \n
            • Must be equipped with independent mechanical ventilation<\/strong>;<\/li>\n
            • Do not share ventilation systems with smoke extraction or building air-conditioning systems.<\/li>\n<\/ul>\n
              \uff083\uff09Critical Projects Should Use Fiber-Optic Winding Temperature Monitoring<\/strong><\/span><\/h4>\n
              Do not rely only on top oil temperature measurement<\/strong>.<\/p>\n
              The winding hot spot temperature<\/strong> is the real \u201cbody temperature\u201d of the transformer. It reflects the thermal condition inside the transformer more accurately than oil temperature.<\/p>\n
              In recent years, the cost of fiber-optic temperature monitoring has decreased significantly. For critical transformers above 2000kVA, this investment is worthwhile.<\/p>\n
              \uff084\uff09 Connect Temperature Monitoring Data to the Management System and Enable Trend Warnings<\/strong><\/span><\/h4>\n
              Many failures do not happen suddenly.<\/p>\n
              If the system can identify a continuous temperature increase before reaching the alarm threshold and provide a warning such as:<\/p>\n
              \u201cWinding temperature has increased by 5\u2103 over the past week. Please check ventilation conditions.\u201d<\/p>\n
              Many shutdown incidents can be prevented in advance.<\/p>\n
              2. Insulation Aging: The Silent \u201cLife Killer\u201d \u2014 Often Discovered Too Late<\/strong><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
              <\/div>\n
              \"\"<\/div>\n
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              Abnormal temperature rise usually triggers an alarm light, but insulation aging<\/strong> is silent.<\/p>\n
              The transformer\u2019s internal insulation system<\/strong> \u2014 including inter-turn insulation, layer insulation, main insulation, and lead insulation \u2014 continuously suffers from the combined effects of electrical stress<\/strong>, thermal stress<\/strong>, mechanical stress<\/strong>, and chemical stress<\/strong>. Its performance gradually declines over years of operation.<\/p>\n
              Once the insulation condition reaches a critical point, it may trigger a chain reaction:<\/p>\n
              Partial discharge \u2192 Inter-turn short circuit \u2192 Main insulation breakdown<\/strong><\/p>\n
              2.1Case: Insulation Risk Caused by Thermal Cycling in a Chile PV Project<\/strong><\/span><\/h3>\n
              The project used multiple 33kV\/0.8kV box-type step-up transformers, each rated at 2000kVA. The equipment had been operating for more than one year without any protection trips.<\/p>\n
              During routine dissolved gas analysis (DGA)<\/strong> testing, two transformers were found to have significantly elevated acetylene (C\u2082H\u2082)<\/strong> levels. Although the values had not yet reached the alarm threshold, the trend was abnormal.<\/p>\n
              Root Cause Investigation:<\/h3>\n
              The root cause was related to the natural operating characteristics of photovoltaic plants:<\/p>\n
              Sunrise: rapid increase from zero load to full load
              Midday: maximum power generation
              Sunset: rapid reduction back to zero load<\/p>\n
              This creates one complete thermal cycle<\/strong> every day.<\/p>\n
              During high-temperature summer periods, daily winding temperature fluctuations could reach 40\u201350\u2103.<\/p>\n
              Long-term thermal cycling resulted in:<\/p>\n
                \n
              • Different thermal expansion coefficients<\/strong> between copper conductors and insulation materials, causing small relative movements<\/strong>;<\/li>\n
              • Gradual reduction of degree of polymerization (DP)<\/strong> of insulating paper, as high temperature accelerates cellulose degradation;<\/li>\n
              • If the winding clamping force<\/strong> was insufficient, looseness could develop, causing partial discharge<\/strong> and accelerating insulation damage.<\/li>\n<\/ul>\n
                Key Lesson:<\/p>\n
                The daily load cycling<\/strong> of PV transformers and the continuous high-load operation<\/strong> of industrial transformers create completely different insulation damage mechanisms.<\/p>\n
                They cannot be evaluated using the same design assumptions.<\/p>\n
                2.2Common Field Manifestations of Insulation Aging<\/strong><\/span><\/h3>\n
                \n
                \n\n\n\n\n\n\n\n\n
                Aging Factor<\/th>\nCommon Site Symptoms<\/th>\nRoot Cause<\/th>\nConsequences<\/th>\n<\/tr>\n<\/thead>\n
                Thermal aging<\/strong><\/td>\nContinuous increase of CO\/CO\u2082 in oil; darker insulation paper color<\/td>\nLong-term overheating (undersized selection \/ insufficient cooling)<\/td>\nReduced insulation strength and shortened service life<\/td>\n<\/tr>\n
                Moisture ingress<\/strong><\/td>\nReduced oil breakdown voltage; moisture content >30ppm<\/strong><\/td>\nBreather failure \/ aging seals \/ moisture introduced during installation<\/td>\nSignificant reduction in breakdown voltage and accelerated paper insulation degradation<\/td>\n<\/tr>\n
                Partial discharge<\/strong><\/td>\nUltrasonic detection signals; increasing C\u2082H\u2082 content in oil<\/td>\nWinding looseness \/ sharp-point discharge \/ internal air gaps \/ floating potential<\/td>\nGradual erosion of insulation, developing into inter-turn or main insulation breakdown<\/td>\n<\/tr>\n
                Oil oxidation<\/strong><\/td>\nDarker oil color; increased acid value<\/strong>; reduced interfacial tension<\/strong><\/td>\nHigh temperature + oxygen exposure (poor oil conservator sealing)<\/td>\nOverall oil performance degradation and accelerated insulation aging<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n
                2.3Combined Testing Methods for Early Insulation Problem Detection<\/strong><\/span><\/h3>\n
                \uff081\uff09Dissolved Gas Analysis (DGA)<\/strong><\/span><\/h4>\n
                Recommended once every six months.<\/p>\n
                Key monitoring parameters:<\/p>\n
                  \n
                • C\u2082H\u2082 (acetylene)<\/strong><\/li>\n
                • CO<\/strong><\/li>\n
                • CO\u2082<\/strong><\/li>\n
                • Total hydrocarbons<\/strong><\/li>\n<\/ul>\n
                  A single abnormal result is important, but trend analysis is even more important<\/strong>.<\/p>\n
                  For example, if the acetylene level of one transformer continues increasing for two consecutive quarters, it should be treated as a warning even if it is still below the official limit.<\/p>\n
                  \uff082\uff09Insulation Resistance and Dielectric Loss Testing<\/strong><\/span><\/h4>\n
                  Recommended annually.<\/p>\n
                  Used to evaluate:<\/p>\n
                    \n
                  • Overall moisture condition;<\/li>\n
                  • Insulation aging condition.<\/li>\n<\/ul>\n
                    During testing, record:<\/p>\n
                      \n
                    • Ambient temperature;<\/li>\n
                    • Humidity;<\/li>\n
                    • Transformer winding temperature.<\/li>\n<\/ul>\n
                      Insulation resistance changes significantly with temperature. Test data without temperature correction has limited comparison value.<\/p>\n
                      \uff083\uff09Partial Discharge Testing (Ultrasonic or High-Frequency Current Method)<\/strong><\/span><\/h4>\n
                      Online monitoring without shutdown.<\/p>\n
                      For critical projects, it is recommended to perform a baseline test six months after commissioning<\/strong>, followed by annual comparison.<\/p>\n
                      \uff084\uff09Establish a \u201cOne Transformer, One File\u201d Operation Record<\/strong><\/span><\/h4>\n
                      All information should be archived:<\/p>\n
                        \n
                      • Factory test results;<\/li>\n
                      • Installation and commissioning records;<\/li>\n
                      • Routine inspection records;<\/li>\n
                      • Oil test results;<\/li>\n
                      • Load operation history.<\/li>\n<\/ul>\n
                        Only with sufficient historical data<\/strong> can engineers accurately distinguish between:<\/p>\n
                        \u201cnormal aging\u201d and \u201cabnormal risk.\u201d<\/p>\n
                        3. Main Reference Standards for Transformer Fault Evaluation<\/strong><\/span><\/h2>\n
                        Actual engineering assessments usually consider:<\/p>\n
                          \n
                        • IEC 60076 series<\/strong> (Power Transformers)<\/li>\n
                        • IEC 60599<\/strong> (Dissolved Gas Analysis of Oil-Immersed Transformers)<\/li>\n
                        • IEEE C57 series<\/strong> (Operation and Maintenance Guidelines)<\/li>\n<\/ul>\n
                          Different projects may have different technical requirements, but the core principle remains the same:<\/p>\n
                          Identify risks in advance by analyzing trends in:<\/p>\n
                            \n
                          • Temperature<\/strong><\/li>\n
                          • Insulation condition<\/strong><\/li>\n
                          • Oil quality<\/strong><\/li>\n
                          • Electrical performance<\/strong><\/li>\n<\/ul>\n
                            4. Oil Leakage Fault: Small Problems Should Not Be Ignored<\/strong><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
                            \"\"<\/div>\n
                            \n
                            Oil-immersed transformer oil leakage<\/strong> is a common issue in outdoor projects.<\/p>\n
                            Many site personnel consider minor oil seepage as \u201cnot serious\u201d and choose to continue operation temporarily. However, from an engineering perspective, any oil leakage should be addressed immediately and should not be delayed.<\/p>\n
                            Transformer oil has two critical functions:<\/p>\n